A newly proposed envelope modulator (EM) which has three outstanding features is presented to increase the efficiency of an RF power amplifier. There are three bottlenecks to design the EM. One is the boosting capability which drives the voltage larger than the battery voltage. Another is a wide bandwidth property that can follow a high frequency envelope signal. The other is that the EM should have a high efficiency property while satisfies the above properties. In order to supply an output voltage higher than the input voltage while providing low-frequency power in the EM, a low frequency converter (LFC) is designed as a single-inductor dual-output (SIDO) converter. Thanks to the SIDO converter, the EM does not require an additional boost converter. In addition, a high-frequency converter (HFC) with a wide bandwidth capability is also proposed. The proposed compensation method is called as an average current assisted (ACA) compensation method. These two converters, the SIDO converter and the HFC, are combined in parallel without an AC coupling capacitor by employing a low- frequency current balancing (LFCB) technique. The chip is imple-mented in a 0.18μm CMOS process and achieves 86.5% peak efficiency while tracking a 10MHz Long Term Evolution (LTE) envelope signal.
본 논문에서는 RF power amplifier의 높은 효율을 달성하기 위한 envelope modulator (EM)를 제안하였습니다. 특히 제안된 modulator는 battery 전압보다 높은 전압을 공급하면서 동시에 저주파대역의 power를 공급할 수 있도록 single-inductor dual-output (SIDO) 구조로 설계가 되었습니다. 이러한 SIDO 구조 덕분에 제안하는 EM은 추가적인 boost converter가 필요 없게 되었습니다. 또한 광대역 특성을 달성할 수 있도록 새로운 방식의 보상방법을 제안하였습니다. 이러한 광대역 converter는 고주파 대역의 power를 공급할 수 있고 SIDO 구조와 coupling capacitor 없이 low-frequency current balancing(LFCB) technique을 이용하여 병렬 연결 됨으로써 높은 효율을 달성할 수 있었습니다.
